Mystery of dolphin and penguin deaths

Scientists searching for the cause of the mass deaths of dolphins and pelicans off the coast of Peru think they know what killed the pelicans.

After weeks of study, investigators say they think they know why the 4450 pelicans have died: hotter than usual ocean temperatures have driven a type of anchovy deeper into the sea, beyond the reach of many young pelicans.

But scientists studying the deaths of hundreds of dolphins and porpoises from early February to mid-April say it remains a mystery, due in part to the government's slowness in investigating the phenomenon.

They say the deaths of the dolphins and pelicans were unrelated and it was a coincidence that they happened around the same time.

Authorities were so late in gathering tissue from the mammals that crucial clues were lost, said the scientist heading the dolphin death probe, Armando Hung, head of the molecular biology lab at Cayetano Heredia University.

From the end of January, daily catches of about five tonnes of anchovies a day by fishermen in the northern region of Lambayeque dwindled after they began finding the small fish dead on the beach, said Fernando Nique, president of the Puerto Eten fishermen's association.

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"After that, we haven't seen any more anchovies," he said.

Patricia Majluf, a biologist and former deputy fisheries minister, said that tongues of warm water reach into coastal zones, driving anchovies deeper underwater where many birds can't reach them.

"For a coast as dynamic as ours, it's not rare that this occurs," said Majluf. "It looks ugly because this has occurred at the same time and place [as the dolphin deaths]."

A biologist at the National University of Trujillo, Carlos Bocanegra, said his analysis of 10 dying pelicans last week supports the theory. Their digestive tracts were either empty or had the remains of fish pelicans don't normally eat.

Scientists say the dead pelicans are generally young, around three years old, an age in which they do not dive as deep as adults.

Ocean temperatures in the region, said Bocanegra, are 6 degrees above normal for this time of year, Peru's autumn.

Similar pelican die-offs have happened in 1982-1983 and in 1997-1998 when the El Nino meteorological phenomena warmed the ocean, Bocanegra said.

The dolphin die-off remains a mystery.

Hung told The Associated Press that lab tests have so far ruled out a number of bacterial infections as the cause.

Because the dolphins were so decomposed, Hung said, it was impossible to rule out a theory promoted by the sea mammal conservation group Orca, which initially publicised the dolphin die-off. Its director, Carlos Yaipen, says he believes the cetaceans were killed by shock waves generated by acoustic "explosions" used to test the sea bed for oil deposits.

Yaipen says he found dolphins with broken bones in their ears, internal hemorrhages and some of their organs collapsed. He described his findings at a congressional hearing on Tuesday, saying he encountered the first batch on February 12.

The government agency in charge of the investigation, the Peruvian Sea Institute (IMARPE), did not explain the delay in obtaining dolphin samples for testing.

"At the moment I have no answer," agency spokesman Vicente Palomino said on Tuesday.

Government officials have said they have no evidence the dolphin deaths are related to seismic oil exploration work that was carried out off northern Peru between February and April.

Hundreds of dolphins have at times turned up dead on beaches in various parts of the world, though the number in northern Peru was particularly high.

Scientists have said that agrochemical runoff from rivers or heavy metals from upstream mining could be potential factors in Peru.

However, IMARPE's director, Raul Castillo, said Tuesday that testing had ruled out heavy metals, pesticides and algae-related biotoxins.

"One of the things we do know is just how fragile we have discovered our ecosystems have become," said Sue Rocca, a US-based marine biologist with the Whale and Dolphin Conservation Society. She said blooms of algae or other biotoxins can affect marine mammals and could be involved.